PROJECT SUMMARY/ABSTRACT Candidate My career goal is to direct a successful laboratory in academia, incorporating cellular, animal, and clinical research to address the impact of the innate immune system on obesity and associated metabolic disorders and the impact of nutrients have on immune cell function. I am applying for the Mentored Career Development Award because it offers an excellent opportunity to transition into an independent investigator. Currently I am a post-doctoral trainee in Dr. Alyssa Hasty's laboratory where I have been able to enhance my molecular techniques and gain experience working with immune cells and animal models of obesity and hyperlipidemia. I have been able to establish my own independent research project aimed at the role of hepatic CD8+ T cells in the development of non-alcoholic fatty liver disease. A number of research skills will be obtained under the present proposal, including RNA sequencing, antibody depletion, adoptive cell transfer studies, and flow cytometry. Also under the mentorship of Dr. Hasty, I will continue to obtain training in scientific communication and professional skills, necessary to become an independent investigator. The scientific environment of Vanderbilt University Medical Center is ideally suited to help me achieve my long career goal to study the immune system and metabolic disease. There are numerous shared resources and core facilities (VANTAGE core, Flow cytometry core) and a vast number of collaborative opportunities available. My previous training opportunities and scientific skills have provided me with a solid background in obesity, diabetes, cardiovascular disease, and nonalcoholic fatty liver disease, necessary to execute my proposed studies. Thus, the knowledge and scientific skills obtained during this training award will help prepare me for my future goal of becoming an independent research scientist in academia. Abstract With the vast increase of metabolic disease, nonalcoholic fatty liver disease (NAFLD) is progressively more common in today's society. NAFLD ranges from hepatic steatosis to cirrhosis. Nonalcoholic steatohepatitis (NASH) is characterized by hepatic steatosis and mixed inflammatory cell infiltration and is a major predictor of fibrotic progression. Recently, NASH has been identified as a risk factor for cardiovascular disease. It is well known that immune cells are key contributors to inflammation and fibrosis. While much attention has been placed on the role of kupffer cells in NAFLD, limited attention has been placed on the subpopulations of lymphocytes and their contribution to NAFLD. Under obese conditions, CD8+ T cells have been found to regulate macrophage infiltration in adipose tissue. Our preliminary data are the first to demonstrate that hyperlipidemia induces an early infiltration of hepatic CD8+ T cells that express a unique Th2 and cytotoxic phenotype. This hepatic lymphocyte infiltration correlates with an increase in hepatic inflammatory monocytes and fibrogenic markers. However, the distinct role of these immune cells in NASH is unclear. Thus, the Specific Aims of this project are: 1) To identify the phenotype of hepatic CD8+ T-cell populations during the transition from steatosis to NASH; 2) To determine in vivo the extent to which CD8+ T-cells impact the development of NASH; 3)To determine in vivo the extent to which IL-10 impacts the transition from hepatic steatosis to NASH. Our hypotheses are 1) early infiltrating CD8+ T-cells express a cytotoxic and Th2 phenotype which drives the recruitment and the profibrogenic phenotype in macrophages; 2) depletion of CD8+ T cells will reduce the recruitment and profibrogenic phenotype of macrophages; while addition of CD8+ T cells will increase the profibrogenic phenotype of macrophages under conditions of hepatic steatosis; 3) depletion of IL-10 will decrease the profibrogenic phenotype in hepatic macrophages under NAFLD conditions. Data obtained from this proposal are expected to provide critical insight for the potential development of therapeutic targets for the prevention and treatment of NASH, and reduce health care costs related to these disorders.